Indicies have a Date and Time for change, but there are no changes posted.
Example: The Investor Monthly Index for Coinbase was last updated on December 01, 2020 1:20 AM EST (UTC 6:20 AM) and November 26, 2020 1:20 AM EST (UTC 6:20 AM)
The Investor Monthly Index for Coinbase next update will be on January 01, 2021 1:20 AM EST (UTC 6:20 AM)
The last Date of Change recorded though is still November 30, 2020 not December 31, 2020 (see photo). Is this a glitch, something due to the change in year or an extra day needed, which would technically be updated on January 02, 2021?